Do I really have to use premium gas on a 240????

[mattscar]

it said in the manual premium gas is required, but ive been using unleaded, is this ok?

[sith_killer_99]

I ran regular in my old engine for a long time, over 18 months and had no problems.

HOWEVER....I ran all 3 grades with my newer engine and there in a noticable difference in performance, especially with fuel economy! Overall it is actually cheaper for me to run premium, as I get better gas milage. I ran 2 tanks of each grade, starting with premium and working my way down to regular.

Yes, I ran the figures and it does make that much of a difference in my car. Though every car will be slightly different, mine performs better with premium, averaging just shy of 26 mpg (city/highway) with premium.

[morpheus78]

I can second this. On 87 my car runs fine, but there is a performance loss you can feel, and the car sucks fuel. With 93 its a whole different ball game.

[mirra32]

i ran the cheap stuff....and my car would keep dying on me....driving would be ok but when back at idle it would die.....even if i use medium grade.....so i use premi all the time...car acts great.....smooth idle and all.....my car is very picky....lol

[Black95s14]

Mine stoped knocking and pinging when i started 93, 117k miles and counting, i noticed a big difference

[ricebike]

yup, those knock sensors would do that to u guys... thank goodness I got the KA24E.

maybe decarbonize the combustion chambers to help your car from not pinging as much when u r strapped to using midgrade?

[thejapino]

WOW!!! you guys got 93 octane? i hate Cali. no i love it

[Dopefish]

Wow, I never realized they requested premium... I've always run the cheap stuff.

My knock sensor is bad too but I used a megaohm 1/2 watt resistor to override it (Not sure if it has yet, just did it yesterday).

I'll fill up with Premium (93) today and see if I notice any gains.

~Kris

[BradC]

The car calls for 91+ octane due to the aggressive timing map in the ECU. If you're car does not perform worse with 87 and better with 91, there's something wrong with your car. I could be that it's pulling timing no matter what octane you use due to carbon buildup in the combustion chambers which increases "pressure" on the fuel which makes it ignate earilier than optimal. This is called pinging or detenation. The knock sensor senses pinging and retards timing appropreitely. This results in less power. If you're car needs a tune-up or has a lot of carbon build-up you will not notice a difference in octane levels.

[glitched]

the higher the octane of a gas, the higher the gas's resiance to early detonation at high temperatures. Its completely fine to use a lower octane gas when you are on a budget because the timing will be retarted just a bit resulting in less power and sometimes mileage. In the colder winter months somtimes this may not even happen. When u speak of losing gas mileage, are you using gas with 10% ethanol? When ethanol is added to gasoline it looses a small percentage of efficency, lowring your gas mileage, however the higher octane resulting from adding ethanol may sometimes make up for it. (example: an 89 with 10% ethanol at the same cost of 87 without ethanol may get the same mileage).

anyway just remember if ur on a budget, its ok to go 87. and try to avoid gas with 10% ethanol added, but if u must, get the higher octane then. (around here gas with ethanol added costs the same no matter what octane)

[Dopefish]

The car calls for 91+ octane due to the aggressive timing map in the ECU. If you're car does not perform worse with 87 and better with 91, there's something wrong with your car. I could be that it's pulling timing no matter what octane you use due to carbon buildup in the combustion chambers which increases "pressure" on the fuel which makes it ignate earilier than optimal. This is called pinging or detenation. The knock sensor senses pinging and retards timing appropreitely. This results in less power. If you're car needs a tune-up or has a lot of carbon build-up you will not notice a difference in octane levels.

I dont think I have excessive carbon build up, even my exhaust tubing was rather clean... although the history of my car is shady as the previous owner wasnt really knowledgable about car care.

I know my timing isnt optimal due to my knock sensor being bad but I'm working to either fix that or at least fake it with a resistor in the mean time. :/

~Kris

[180fan]

Talkin on the inside of your cylinders. I'd assume with 100k+ the carbon deposits must be pretty heavy. The 3 SR's I've torn apart all had less than 45k on them and the combustion chambers were heavily coated with carbon deposits. It's still good maintainence.

No, higher octane = higher power is a myth. Higher octane gives higher resistance to predetonation and slower rate of burn than lower octanes.

[steaminhotryce]

Interesting.... Thanks guys. I learned something new today. NICO is the best! I'll start using Premium from now on and see if I get better gas mileage. I've been using regular 76 and I get 22-24. Hope premium would make a significant difference.

[BradC]

FYI i get consistant 26.8-27.6 MPG with premium. I have a auto and I do mostly highway driving.

[rsmithdrift]

THERE IS NO PERFORMANCE OR GAS MILEAGE DIFFERENCE BETWEEN 87 AND 93 OCTANE!!!!!!!!

The only difference is that higher octane gas is less prone to detonation because it burns slower.

The only time you will notice a difference is if your timing is advanced above 25* (factory is 20*) or if you have turbo. Higher octane will mean you can run higher boost pressure meaning more power. The gas itself does nothing to increase power or gas mileage.

And FYI, I have my Z advanced to 25* and I can run 89 octane w/o any difference from 93+. Above 89 octane the z performs the same regardless. I have run 98 octane and it gives no performance boost whatsoever over 89. Advancing the timing and running 89+ though did make a quite noticable difference. I get an extra 3mpg from before and I'd say 5hp. I'd recomend it to anyone, very worth it. My 240 is at 20* and I run 87 octane regularly. I am going to have it advanced in a few weeks though.

If your car is stock, the only difference you will feel is psychological. You'd be amazed the difference placebo can make in most people.

[GoinTopless240]

Just a word from what I've heard. The higher the octane the complete the burn in the cylinder. Meaning less carbon buildup. Also the cleaner the burn will mean less unburnt fuel lurking in the camber. The cleaner burn also results in a cooler temp in the combustion chamber. As we all know, the cooler temp means the air is more dense in the chamber and hence more power with each stroke. This is why you get better fuel mileage when you run premium fuel. I get as much as 4 mpg on premium. My car has only seen 87 octane twice and it was when my wife put gas in it. Needless to say she has been banned from putting fuel in it from now on. Hope this helps clear up any questions. As far as the timing and knock sensors are concerned you guys are right on. Great group here.

[9095240SXDUCK]

I have used 93 for every 240sx I have ever owned! On the S14 it saids it on the Gas Door to use 93 for better performance!

[9095240SXDUCK]

THERE IS NO PERFORMANCE OR GAS MILEAGE DIFFERENCE BETWEEN 87 AND 93 OCTANE!!!!!!!!

The only difference is that higher octane gas is less prone to detonation because it burns slower.

The only time you will notice a difference is if your timing is advanced above 25* (factory is 20*) or if you have turbo. Higher octane will mean you can run higher boost pressure meaning more power. The gas itself does nothing to increase power or gas mileage.

And FYI, I have my Z advanced to 25* and I can run 89 octane w/o any difference from 93+. Above 89 octane the z performs the same regardless. I have run 98 octane and it gives no performance boost whatsoever over 89. Advancing the timing and running 89+ though did make a quite noticable difference. I get an extra 3mpg from before and I'd say 5hp. I'd recomend it to anyone, very worth it. My 240 is at 20* and I run 87 octane regularly. I am going to have it advanced in a few weeks though.

If your car is stock, the only difference you will feel is psychological. You'd be amazed the difference placebo can make in most people.

Sorry to say this but you are the one that is

I would think Nissan Know more about their engine then any of us. Also, I have try to run this on the Track before useing 93 and 87! Also They don't gain anything from printing saying to use 93!

[Chezedik]

There CAN be a difference in performance, but no, there will be 0 difference in economy. That is based strictly on the heat content of the fuel. Maybe with xylene it will change a minute amount, but nothing you will notice in calculations using the odometer.

[180fan]

I have yet to see gas be the cause of more power. In the quest for power, there will be things that will require higher octane gas to prevent damage, but if your engine is running as it should be in stock trim, you will not get more power.

[Chezedik]

It's all in the chemistry. You must look for a proper balance of Cetane, Octane and Low Heat Value. The thing is that the refiners know their ****, and when they try to pimp a fuel, they need to make sure their stuff performs.

EDIT: No, in stock trim, it will not perform better for the most part. Only because, due to proper timing control, you should not have problems with combustion chamber vapor pressure.